Measurement of the J/? Polarization with Respect to the Event Plane in Pb-Pb Collisions at the LHC



Acharya, S, Adamova, D, Adler, A, Rinella, G Aglieri, Agnello, M, Agrawal, N, Ahammed, Z, Ahmad, S, Ahn, SU, Ahuja, I
et al (show 1022 more authors) (2023) Measurement of the J/? Polarization with Respect to the Event Plane in Pb-Pb Collisions at the LHC PHYSICAL REVIEW LETTERS, 131 (4). 042303-. ISSN 0031-9007, 1079-7114

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Abstract

We study the polarization of inclusive J/ψ produced in Pb-Pb collisions at sNN=5.02 TeV at the LHC in the dimuon channel, via the measurement of the angular distribution of its decay products. We perform the study in the rapidity region 2.5<y<4, for three transverse momentum intervals (2<pT<4, 4<pT<6, 6<pT<10 GeV/c) and as a function of the centrality of the collision for 2<pT<6 GeV/c. For the first time, the polarization is measured with respect to the event plane of the collision, by considering the angle between the positive-charge decay muon in the J/ψ rest frame and the axis perpendicular to the event-plane vector in the laboratory system. A small transverse polarization is measured, with a significance reaching 3.9σ at low pT and for intermediate centrality values. The polarization could be connected with the behavior of the quark-gluon plasma, formed in Pb-Pb collisions, as a rotating fluid with large vorticity, as well as with the existence of a strong magnetic field in the early stage of its formation.

Item Type: Article
Uncontrolled Keywords: ALICE Collaboration
Divisions: Faculty of Science & Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 03 Oct 2023 15:14
Last Modified: 23 May 2026 07:41
DOI: 10.1103/PhysRevLett.131.042303
Open Access URL: https://doi.org/10.1103/PhysRevLett.131.042303
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3173371
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